This study will investigate the provision of health care services to a statewide population of HIV-positive Medicaid participants whose service needs are complicated by major psychiatric comorbidities, particularly schizophrenia and schizoaffective disorder. The overall objective is to generate much-needed knowledge about care of these persons so that policies and programs, which have largely been developed on the basis of findings from inpatient samples, can better address their complex needs. The research will use a unique database created by merging multiple New Jersey Medicaid administrative and claims records with HIV/AIDS Registry data, covering the years 1988-1999 for 8,996 individuals, including (according to preliminary classifications) 577 who received at least one inpatient or two outpatient diagnoses with schizophrenia or schizoaffective disorder, with a mean of 55 encounters with schizophrenia diagnoses. We will also examine, as a secondary focus, individuals diagnosed with mood disorders including bipolar disorder and recurrent major depressive disorder, and will explore the association between combinations of psychiatric and substance abuse comorbidities and use of health care services. The study will examine the types and combinations of psychiatric diagnoses reported by health care providers during health care encounters with HIV+ persons on Medicaid; refine claims-based diagnostic classifications; explore the impact of psychiatric conditions on the types and amounts of health care services used over the course of HIV; analyze receipt of mental health services and the type and consistency over time of psychotropic use; and examine the relationship between comorbid major mental disorders, with and without comorbid substance abuse, and patterns of antiretroviral therapy including type of regimen, incidence of use, consistency of use over time, and dropout from treatment. Results of these analyses will provide an important information base for the development of policies and programs to improve the care of this under-studied group within the population living with HIV.